STRaman Technology: Raman for See Through Material Identification

Importance of the topic

Raman spectroscopy is a powerful nondestructive analytical technique widely used in pharmaceuticals, chemical manufacturing, security screening and biomedical research. However, conventional Raman systems face limitations when measuring materials enclosed in opaque or diffusely scattering containers, or when analyzing heterogeneous, photolabile or thermolabile samples. The ability to probe through scattering media without sample damage and with high reproducibility addresses critical needs in quality control, forensic analysis and in situ process monitoring.

Objectives and study overview

This application note introduces STRaman™ technology as implemented in the i-Raman® Pro ST Analyzer. The goal is to demonstrate how a wide-area illumination and collection design extends the sampling depth, enhances subsurface Raman signal, and reduces power density, enabling robust identification of compounds inside non-transparent packaging and improved measurements of sensitive or heterogeneous samples.

Methodology

The report contrasts three configurations: traditional confocal Raman, Spatially Offset Raman Spectroscopy (SORS), and the See-Through STRaman approach. STRaman employs a large probe footprint to collect diffusely scattered Raman photons from deeper layers. Spectra were acquired using a 785 nm, 450 mW laser on the i-Raman Pro ST system. Raw intensity data were corrected according to a NIST‐based procedure.

Used Instrumentation

• i-Raman Pro ST spectrometer
• 785 nm excitation laser, 450 mW output
• NIST SRM-based intensity correction protocol

Main results and discussion

• Sodium benzoate identification through white polyethylene demonstrated strong content peaks after container subtraction versus standard backscatter dominated by filler signals.
• D-(+) glucose detection through manila envelopes overcame cellulose fluorescence that masked analyte signals in confocal mode.
• Coated pharmaceutical tablets (e.g., Advil) yielded clear drug signatures under STRaman, whereas conventional probes were dominated by sugar coating peaks.
• Measurement of photolabile gun powder and thermolabile samples at full laser power showed key sulfur and nitrate bands without sample damage.
• Transcutaneous analysis of human tibia and muscle produced distinct mineral and protein signatures, validating in vivo tissue probing.
• Heterogeneous samples (Excedrin migraine tablets) and large crystals (xylitol) measured at multiple positions gave highly reproducible Hit Quality Indices with zero false negatives under STRaman, compared to wide HQI distributions in confocal mode.

Benefits and practical applications

• Noninvasive through-container identification for incoming QC and security screening
• Safe analysis of photolabile and thermolabile compounds
• Enhanced reproducibility for heterogeneous formulations and crystalline materials
• Portable field deployable system for rapid on-site screening
• Potential for in vivo biomedical diagnostics and process monitoring

Future trends and applications

Advances may include integration of machine learning for real-time spectral matching, handheld STRaman devices, deeper subsurface diagnostics in biomedical and cultural heritage applications, inline monitoring of manufacturing processes, and extension to ceramics, polymers and composite materials.

Conclusion

STRaman technology significantly broadens the capabilities of Raman spectroscopy by enabling reliable analysis through diffusely scattering media, reducing sampling bias in heterogeneous samples, and preserving sensitive materials under analysis. This high-throughput, portable approach delivers rapid, accurate identification in a wide range of industrial, security and research contexts.

References

1. Matousek P, Clark IP, Draper ERC, Morris MD, Goodship AE, Everall N, Towrie M, Finney WF, Parker AW. Subsurface Probing in Diffusely Scattering Media Using Spatially Offset Raman Spectroscopy. Appl Spectrosc. 59:393–400 (2005)
2. Choquette SJ, Etz ES, Hurst WS, Blackburn DH, Leigh SD. Relative Intensity Correction of Raman Spectrometers: NIST SRMs 2241–2243 for 785 nm, 532 nm, and 488 nm/514.5 nm Excitation. Appl Spectrosc. 61:117–129 (2007)
3. Matousek P, Draper ERC, Goodship AE, Clark IP, Ronayne KL, Parker AW. Noninvasive Raman Spectroscopy of Human Tissue In Vivo. Appl Spectrosc. 60:758–763 (2006)
4. Ling XF, Xu YZ, Weng SF, Li WH, Zhi X, Hammaker RM, Fateley WG, Wang F, Zhou XS, Soloway RD, Ferraro JR, Wu JG. Investigation of Normal and Malignant Tissue Samples from the Human Stomach Using Fourier Transform Raman Spectroscopy. Appl Spectrosc. 56:570–573 (2002)